Recently, electronic devices having high-speed processing performances and using higher frequencies have been increasing and therefore electronic components used for such electronic devices must also have high-speed processing performances and use higher frequencies. Since the miniaturization of electronic devices has been advancing, electronic components must be miniaturized and mounted in high density.
In order to meet such requirements, multilayered circuit boards for mounting semiconductor elements and various electronic elements are employed. In such multilayered circuit boards, conductor circuits and electronic functional elements are arranged in a substrate, and therefore electronic components can be miniaturized.
A principal material for the multilayered circuit board includes aluminum. Since the firing temperature of aluminum is 1500-1600° C., refractory metals such as Mo, Mo—Mn, and W must be used for conductor materials of circuits contained in alumina multilayered circuit boards. However, there is a problem in that such refractory metals are expensive and have a high electrical resistance.
Therefore, there is a large demand for using an inexpensive metal, for the conductor materials, having a smaller electrical resistance than those of the above refractory metals, wherein the inexpensive metal includes, for example, copper. For example, in Japanese Unexamined Patent Application Publication No. 5-238774, in order to realize the use of copper for the conductor materials, a substrate material such as a glass ceramic and crystallized glass which are capable of being fired at 1000° C. or less is proposed. In Japanese Unexamined Patent Application Publication No. 8-34668, in consideration of the connection to semiconductor devices such as Si chips, the application of a ceramic having a thermal expansion coefficient close to that of Si to multilayered circuit board materials is proposed. However, there is a problem in that such substrate materials have a small mechanical strength and a small Q-factor and that the kinds and the ratio of deposited crystal phases are affected by the firing process.
Chip components such as semiconductor devices are mounted on ceramic multilayer substrates including an insulating ceramic composition in some cases. On the other hand, ceramic multilayer substrates having chip components thereon are mounted on circuit boards such as printed circuit boards for ceramic electronic components. Thus, input/output terminals for inputting/outputting signals are essential for such ceramic electronic components and the distance between the input/output terminals must be small due to the miniaturization of electronic components.
Therefore, insulating ceramics produced by firing insulating ceramic compositions must have high dimensional accuracy. However, insulating ceramics produced by firing conventional insulating ceramic compositions have insufficient dimensional accuracy.
The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide an insulating ceramic composition (1) that is capable of being fired together with a low-melting conductive material such as silver and copper and (2) that can provide an insulating ceramic having a small relative dielectric constant, excellent high-frequency characteristics, and a relatively high thermal expansion coefficient.
It is another object of the present invention to provide an insulating ceramic that is obtained by low-temperature firing and has a small relative dielectric constant, excellent high-frequency characteristics, and a relatively high thermal expansion coefficient.
It is another object of the present invention to provide a ceramic multilayer substrate and ceramic electronic component including an insulating ceramic composition according to the present invention and having excellent high-frequency characteristics and a high-density circuit pattern.
It is another object of the present invention to provide a method for manufacturing a ceramic multilayer substrate that can be obtained by low-temperature firing and has excellent high-frequency characteristics and dimensional accuracy and in which a high-density circuit pattern can be formed.